Improve note inclusion path serialization

One more general comment: there is a much more efficient way to serialize note inclusion paths which would guarantee that we fit into 5MB limit even if a block contained $2^{16}$ output notes. It is quite a bit more involved though - instead of sending a Merkle path with every node, we'd need to send a single partial SMT for an entire block. So, it is not something we should do now, but let's create an issue for this.

_Originally posted by @bobbinth in https://github.com/0xMiden/miden-node/issues/1224#issuecomment-3314557332_